adding-tls-1.2: Change the protocol version to 1.2

[hieuhidro]

Description

• Adding default protocol version to src/Client.php
• Setting up the default protocol to 1.2, since Avatax is is discontinuing support TLS 1.0 & 1.1

How To Reproduce

Steps to reproduce the behavior:

• Goes to admin and config avatax account
• Check the connection status

Expected behavior

• The API connection protocol for Avatax will be updated to version 1.2.

Benefits

• Since Guzzle's Client uses 1.1 as the default protocol, the default protocol is being updated from 1.1 to 1.2.

Additional information

• N/A